The latest generation of medical devices have demanding power requirements such as high rate requirements. Power sources (electrochemical cells, cells or batteries hereinafter) used heretofore for medical applications and other applications have included, for example, cathodes of MnO.sub.2. Such cells have been satisfactory and have exhibited gradually decreasing voltage curves in low rate applications. When utilized in high rate applications the gradual discharge ramp is lost and becomes one in which cell service life ends precipitously with a sharp voltage drop off at end-of-service (EOS). This is unsatisfactory and some means is required for signaling the onset of cell depletion or EOS i.e., monitoring for remaining cell service life.
In general, composite electrodes of different potentials to warn of cell depletion are known in battery technology. For example, U.S. Pat. Nos. 3,757,793 to Doty and Fester; U.S. Pat. No. 4,619,874 to Hayes and Skarstad and U.S. Pat. No. 4,259,415 to Tamura et al relate to composite cathodes.